Topological phases in narrow-band systems

I discuss several novel topological phases in correlated electron systems, realized through spin-orbit interactions and lattice effects especially narrow-band systems. The first realizes the fractional quantum Hall effect using geometric frustration and ferromagnetism to obtain a nearly flat band with a large bandgap and non-zero Chern number. This system can support this effect at high temperatures upon partial filling of the flat band. The second proposal builds upon this system: as the ground state is a fractional quantum Hall state, excitations of this state are anyons when there is an incommensurate filling. The underlying lattice allows access to a new regime in which the anyon gas can form a charged superfluid, including states with intrinsic topological order or that similar to a BCS-type state. The third proposal studies topological crystalline insulators and strain as an effective gauge field on the surface state Dirac fermions. The zero-energy Landau orbitals form a flat band where the high density of states gives rise to the interface superconductivity observed in IV-VI semiconductor multilayers at high temperatures, with non-BCS behavior. A discussion of superconductivity in flat band systems concludes and is contrasted with classic results for a typical electron gas. This work closely parallels that in references [1, 2, 3].

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2015

Author dc:creator

• Tang, Evelyn (Evelyn May Yin)

Advisor dc:contributor.advisor

• Xiao-Gang Wen.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/103220

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/103220